A computer program to automatically control the multileaf collimator

Abstract

A computer program to automatically analyze strip test images for MLC leaf positioning quality assurance was developedand assessed. The program is fed with raw individual segment images in DICOM format supplied by the acceleratorsoftware and it automatically carries out all the steps in the leaf positioning quality control test (image merging, image analysis,storing and reporting). A comprehensive description of the software, that allows a relatively easy implementation, is shown.To check the performance of the program, a series of test fields with intentionally introduced errors were used. The obtainedMeasurement uncertainty of any individual leaf position was lower than 0.15 mm with gantry at 0º. At another gantry angles(90º, 180º and 270º) the dispersion of the measurements was larger, specially towards the external positions of the leafs, probablydue to a slight rotation of the EPID caused by gravity. That reduces the useful area of the MLC to control when gantryangles different from 0º are used. In conclusion, this technique is fast enough to be carried out in a daily basis being also veryprecise and reliable.